In many industries where complex machinery is employed, it is common to form housings for enclosing a multitude of components, such as a gear box housing, in two parts which are originally formed as steel castings and then are machined to provide the desired internal configuration and a peripheral planar mating surface on each component which are traversed by peripherally spaced bolt holes to receive bolts which effect the sealed securement of the two housing parts.
This technique is employed to manufacture gear box housings for aircraft jet engines with the exception that the castings are formed from a magnesium or aluminum alloy or other suitable material due to the necessity of minimizing the weight of the gear box housing. The shafts and gears mounted in such housing are normally lubricated by a continuous flow of pressurized lubricating oil. The slightest leakage anywhere in the hydraulic system creates the risk of bearing failures. More importantly, the gear box housing and the hydraulic system must maintain its sealed relationship through a wide range of temperatures. Temperatures of minus 50.degree. F. are often encountered by jet aircraft flying at altitudes on the order of 30,000 feet. On the other hand, when the aircraft is on the ground and the ground temperature is 100.degree. F., the temperature of the housing and its contained components may reach the level of 400.degree. F. These extreme reversals of temperature, which occur every time the jet aircraft takes off or lands, impose substantial stresses on the gear box housing and cause wear on all components contained therein. Additionally, these stresses are amplified by stresses derived from the gear shafts which are mounted in beatings supported by machined bores within the gear box housing.
From the foregoing, it will be apparent that gear box housings for jet aircraft have a limited life, yet those housings are individually very expensive to manufacture due to their complexity. The total cost of a single front or rear housing is on the order of $20,000. There is a need, therefore, for a repair technique to restore any defective or worn valve housing to its original machined condition without in any manner decreasing the strength or serviceability of the valve housing and accomplishing such repair for a figure on the order of $5,000 or less to provide a substantial economic incentive for repairing such complex metallic components rather than throwing them away.